The effect of stimulus significance on the electrodermal response in chronic schizophrenia

Skin conductance reactivity (SCR) to stimuli made significant for half of each sample and kept innocuous for the other half was compared in schizophrenics, normals, and alcoholics. In every case, trials began with a 5-sec slide presenting four different words and ended 15 sec later with a recorded auditory presentation of one of these words. For half of each sample, stimuli were made significant by requiring subjects to retain the visually given words so that, on hearing the subsequent spoken word, they could immediately repeat one of the words in the last-seen slide other than that just heard (report condition). The remaining subjects only had to sit still and do nothing (simple condition). As predicted, schizophrenics showed smaller, faster habituating SCRs than controls only in the simple condition and resembled controls when the same stimuli were made significant in the report condition. Words were selected a priori for delusional, alcoholic, and neutral content to see whether this would affect SCR. However, posttest interviews revealed that the a priori selections were not successful in establishing differential significance, and SCR accordingly did not vary with content in any group. In all groups, introducing explicit significance markedly increased SCR amplitude, slowed habituation, and heightened spontaneous fluctuation frequency to both visual and auditory stimuli, but did so most markedly to the auditory signals that were closer in time to the significance-creating report.